Searches revealed the 18-year-old, born and raised in the Bavarian capital, "looked intensively" at the subject of "shooting rampages," Andrae said. Officials said they found a book called “Rampage in the Head: Why Students Kill” among his belongings.

It appeared the attacker hacked a young woman’s Facebook account and posted a message to lure people to the mall for a free meal, according to police.